Analía Bellizzi – Chemistry Classes

Ronald Reagan Senior High School

# AS Volumetric Analysis 1-Standard solution of NaOH

#### Preparation of a standard solution of sodium Hydroxide

Background information:

A standard solution is any solution in which we know the exact concentration. A standard solution of a solid can be prepared by weighing a mass of the solid, and dissolving it in a known volume of solution in a volumetric flask. Today, you will prepare a standard solution of sodium hydroxide. Since the dissolution process is exothermic, we will be using this solution in a second lab next class.

Materials:

• Vial with around 2 of NaOH
• 100 o 150 mL Beaker
• Glass rod
• Triple beam balance
• Distilled water

Procedures

1. Measure the mass of the test tube with the NaOH pellets                     …………………..g
2. Measure the mass of the empty 100 ml beaker                                        .………………….g
3. Transfer the pellets from the test tube to the beaker
4. Measure the mass of the beaker with the pellets                                     ……………………g
5. Measure the mass of the test empty test tube with the stopper            …….……………..g
6. Calculate the mass of the pellets by difference in both the test tube and the beaker. The mass should be almost the same in both cases!
7. Record this mass:                                              Mass of NaOH used    .…………………..g
8. Dissolve the pellets in the beaker using distilled water.
9. Pass the solution to the volumetric flask.
10. Rinse the beaker several times to be sure that all the NaOH passed to the volumetric flask
11. Fill out the volumetric flask to “near” the 250 cm3 mark. BE SURE THAT YOU DO NOT OVERPASS THE MARK.
12. Use a rubber stopper to close the volumetric flask
13. Label and save the flask for next lab

Lab Setup (EXPLAIN WHAT YOU DID USING GRAPHS IN THREE OR MORE STEPS)

1)                2)                  3)

Post Lab Questions:

1. Why do you have to prepare the solution in advance?
2. How many grams of NaOH did you use for the solution?
3. How many moles of solute were present in the volume prepared?
4. How many mL of solution did you prepare?
5. Calculate the Molarity of the solution in # moles of NaOH/dm3